The celebration of the Great Feasts of the church year are extended for a number of days, depending upon the particular Feast. Each day of an Afterfeast will have particular hymns assigned to it, continuing the theme of the Feast being celebrated. At each of the divine services during an Afterfeast, the (Gk.) troparion and (Gk.) kontakion of the feast are read or chanted. The (Gk.) canon of the feast will usually be chanted on every day of the Afterfeast (if two canons were chanted on the day of the feast, they will be alternated on the days of the afterfeast). Some of the Great Feasts of the Lord will have a special canon composed of only three odes, called a (Gk.) Triode, which will be chanted at Compline on each day of the Afterfeast.

Most of these Great Feasts also have a day or more of preparation called a Forefeast (those Feasts that are on the moveable Paschal Cycle do not have Forefeasts). Forefeasts and Afterfeasts will affect the structure of the services during the Canonical Hours.

The last day of an Afterfeast is called the Apodosis (Gk. "leave-taking", lit. "giving-back") of the Feast. On the Apodosis, most of the hymns that were chanted on the first day of the Feast are repeated. On the Apodosis of Feasts of the Theotokos, the Epistle and Gospel from the day of the Feast are repeated again at the Divine Liturgy.

Four of these Afterfeasts have a special commemoration on the day following the Feast, called a (Gk.) Synaxis. In this context, a Synaxis commemorates a saint who is intimately bound up with the Feast being celebrated. The four Synaxes are:

Synaxis of Ss. Joachim and Anna (9 September—the day after the Nativity of the Theotokos)

Synaxis of the Theotokos (26 December—the day after the Nativity of our Lord)

Synaxis of the Forerunner (7 January—the day after the Theophany of our Lord)

Synaxis of the Archangel Gabriel (26 March—the day after the Annunciation) If the Annunciation falls during Holy Week the Synaxis is omitted.[6]

Other Great Feasts that have Afterfeasts (although no Forefeasts) are:

^The Forefeast and Afterfeast of the Meeting of the Lord are variable, depending on the date of Pascha that year: the Afterfeast must always end before the beginning of Great Lent.

^The day before Palm Sunday, Lazarus Saturday could be considered a type of Forefeast for Palm Sunday.

^ abIf the Annunciation falls during Holy Week there will be no Forefeast or Afterfeast. This timing is only possible for Orthodox churches who continue to follow the Julian calendar, since March 25 in the Revised Julian calendar falls too early to be that close to even the earliest of Paschas.

^Holy Saturday could be thought of as a Forefeast of Pascha, but the Bright Resurrection of Christ is so far above and beyond the normal level of Great Feasts that it falls into a category all by itself. It does, however have an Afterfeast, and that is why it is treated in this table.

^Mid-Pentecost (Gk.) is unique in that it is a Feast that falls within a Feast (falling as it does within the Afterfeast of Pascha).